Efficient semi-analytical generator of initial stiffness designs for steel frames under seismic loading. Part 1: Fundamental frame

The purpose of this paper is to propose a new efficient semi-analytical generator of initial stiffness designs for a moment-resisting steel building frame under seismic loading. Requirements on interstory drift under seismic loading are often active constraints in the usual structural design practice for steel building frames and simple methods of design and analysis are needed especially in the preliminary design stage. Interstory drifts and ratios of the angles of nodal rotation to the angles of column member rotation are selected as key parameters and specified based upon the designer's intention. A practical design formula for a frame with design variable grouping is proposed as well as one for a basic frame without design variable grouping. A recursive technique is introduced to evaluate the design story shear forces under a set of design-spectrum-compatible earthquakes. Numerical examples are presented to disclose the characteristics of member stiffness distributions and the response characteristics of frames designed by the present method. In the present paper (Part 1), a fundamental design formula is proposed for a simple frame without column elongation. A more practical design formula for a slender frame with column elongation will be presented in the companion paper. (Part 2). © 1997 John Wiley & Sons, Ltd.